[英]Passing arrays as method parameters in Java
以下代碼在Java中使用String的簡單數組。
package javaarray;
final public class Main
{
public void someMethod(String[] str)
{
System.out.println(str[0]+"\t"+str[1]);
}
public static void main(String[] args)
{
String[] str1 = new String[] {"day", "night"};
String[] str2 = {"black", "white"};
//Both of the above statements are valid.
Main main=new Main();
main.someMethod(str1);
main.someMethod(str2);
//We can invoke the method someMethod by supplying both of the above arrays alternatively.
main.someMethod(new String[] { "day", "night" }); //This is also valid as obvious.
main.someMethod({ "black", "white" }); //This is however wrong. The compiler complains "Illegal start of expression not a statement" Why?
}
}
在上面的代碼片段中,我們可以像這樣初始化數組。
String[] str1 = new String[] {"day", "night"};
String[] str2 = {"black", "white"};
我們可以直接將它傳遞給方法,而不是像這樣分配。
main.someMethod(new String[] { "day", "night" });
如果是這樣,那么以下陳述也應該是有效的。
main.someMethod({ "black", "white" });
但編譯器抱怨“非法開始表達而不是聲明”為什么?
根據Java語言規范( 10.6。陣列初始化器 )
可以在聲明中指定數組初始值設定項,也可以將其作為數組創建表達式(第15.10節)的一部分,創建數組並提供一些初始值:
因此,只有兩種方法可以使用數組初始值設定項( {"foo", "bar"}
):
String[] foo = {"foo", "bar"};
new String[] {"foo", "bar"};
您不能將數組初始值設定項用作方法參數。
ArrayCreationExpression: new PrimitiveType DimExprs Dimsopt new ClassOrInterfaceType DimExprs Dimsopt new PrimitiveType Dims ArrayInitializer new ClassOrInterfaceType Dims ArrayInitializer
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